An injured Afghan child at the hospital in Farah province. Photograph: Abdul Malek/AP

US-led air strikes have killed dozens of Afghan people, the Red Cross said today as the Pentagon launched a joint investigation into what appeared one of the deadliest incidents and heaviest civilian losses so far at the hands of coalition forces.

Rohul Amin, the governor of Farah province in west Afghanistan, where the bombing took place during a battle on Monday and Tuesday, said he feared 100 civilians had been killed.

The provincial police chief, Abdul ­Ghafar Watandar, who accused the Taliban of using the civilians as human shields, said the death toll could be even higher, with some local officials claiming it could be up to 200.

If confirmed, those figures could make the strike the worst single most deadliest for Afghan civilians since the start of the campaign to topple the Taliban in 2001.

Jessica Barry, a spokeswoman for the International Committee of the Red Cross, said that when an aid team reached the scene of the air strikes "there women and there were children killed, it seemed they were trying to shelter in houses when they were hit".

The Red Cross team said they saw ruined houses and dozens of human bodies, providing the first international confirmation of the incident. Among those killed was a first aid volunteer for Afghanistan's Red Crescent, who died along with 13 members of his family, Barry said.

The US military rushed to pin the blame for the air strikes on Afghanistan's army and police force.

A spokesman for the US forces in Afghanistan said the bombings had been requested by an Afghan unit after it came under fire in the province of Farah and was "totally unlike" an incident last year, which the UN said had killed 90 civilians, and which damaged relations between the Afghan president, Hamid ­Karzai, and his US allies. "This was not coalition forces. This was Afghan national security forces who called in close air support, a decision that was vetted by the Afghan leadership," said Captain Elizabeth Mathias.

She added that a US investigation team arrived at the site today to assess the aftermath of the attack, which was requested by a US special forces soldier embedded in the Afghan unit.

Karzai, who is in Washington for talks with Barack Obama, said he would raise the issue of civilian deaths at the White House. "The president has termed the loss of civilians unjustifiable and unacceptable, and will raise it with Obama," Karzai's office said.

The police chief Watandar said Taliban guerrillas had herded civilians into houses in the villages of Geraani and Ganj Abad, and these places were then struck by war planes. "The fighting was going on in another village, but the Taliban escaped to these two villages, where they used people as human shields. The air strikes killed about 120 civilians and destroyed 17 houses," he said, admitting, however, that the death toll was imprecise.

Villagers took about 30 bodies to the provincial capital, Farah city, yesterday to prove that dozens had been killed in the strikes. Haji Khudadade, police chief of Bala Bluk district, said police went to the village when local Taliban members began preparing to attack a nearby highway. He also said insurgents had been harassing villagers, forcing them to pay taxes on poppy crops. "They have had a lot of problems with the Taliban. The Taliban captured two local people for not paying their tax and they were only stopped from executing them by the tribal elders," he said.

US-led forces have acknowledged they were involved in fighting and air strikes in the area, saying they are jointly investigating reports of civilian casualties alongside the Afghan authorities.

Civilian deaths are a source of tension between the Afghan and American governments, and Karzai has repeatedly told the US that civilian casualties from air strikes play into the hands of the Taliban.

There were conflicting accounts last night about what happened. One version suggested children, women and elderly people had gone to Geraani to escape fighting between the Taliban and Afghan National Army (ANA) but that the compounds they had sheltered in were bombed. One girl, Shafiqa, who was wounded in the fighting told Associated Press Television News: "We were at home when the bombing started. Seven members of my family were killed."

A US bombing raid in last August at Azizabad caused 90 civilian deaths. The US originally said no civilians died before eventually conceding that 33 people had been killed. The US later issued a directive designed to help lessen the chance of similar mass civilian deaths.

The inquiry into the bombing was announced on the eve of a summit at the White House today between Obama, Karzai and the Pakistan president, Asif Ali Zardari. Karzai yesterday again called on the US for restraint in bombing areas where civilians were at risk. Speaking in Washington, he said Obama's strategy would only work if he ensured Afghans were protected. "This war against terrorism will succeed only if we fight it from a higher platform of morality."

A US spokesman in Afghanistan, Colonel Greg Julian, confirmed that US coalition forces had participated in the fighting on Monday night. "There was an insurgent attack on an ANA group and the ANA called for assistance, and some coalition troops joined them to help fight this group. There was close air support," he told Reuters. He said US and Afghan officials would go to the site today to investigate the reports of deaths.

Mohammad Nieem Qadderdan, a former top official in the district of Bala Baluk, reportedly said he saw dozens of bodies when he went to Geraani. "These houses that were full of children and women and elders were bombed by planes. People are digging through rubble with shovels and hands."

Qadderdan said the civilian casualties were "worse than Azizabad".

Obama, on being elected in November, regarded Afghanistan as top of his foreign policy agenda, but the issue has been superseded by concern about advances by the Taliban in Pakistan.